Method for transmitting and receiving control channel in wireless communication system

ABSTRACT

Provided is a communication system that transmits a control channel using a downlink. The communication system may transmit, to the terminal, transmission information of uplink allocation information that indicates whether uplink allocation information is transmitted using a downlink, and the terminal may determine whether the uplink allocation information is included in a downlink frame, based on the transmission information of uplink allocation information. The base station may transmit, to the terminal, information associated with a resource which has a possibility of being used for transmission of a physical downlink control channel (PDCCH), and the terminal may decode the PDCCH in the resource which has a possibility of being used for transmission of the PDCCH.

RELATED APPLICATIONS

This application is a continuation of PCT/KR2011002927, filed on Apr.22, 2011, which claims the benefit of Korean Patent Application No.10-2010-0040982, filed on Apr. 30, 2010, Korean Patent Application No.10-2010-0079151, filed on Aug. 17, 2010, Korean Patent Application No.10-2010-0082677, filed on Aug. 25, 2010, Korean Patent Application No.10-2010-0100197, filed on Oct. 14, 2010, Korean Patent Application No.10-2010-0100476, filed on Oct. 14, 2010, Korean Patent Application No.10-2010-0109817, filed on Nov. 5, 2010, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a method of transmitting and receivinga control channel in a wireless communication system, and moreparticularly, to a method of transmitting downlink allocationinformation and uplink allocation information using a downlinksub-frame.

BACKGROUND ART

An amount of signal transmitted via a wireless communication network isconstantly increasing. In the near future, a signal of which a volume isseveral times greater than currently used signals will be transmittedvia the wireless communication network.

Recently, a technology that improves efficiency in data transmissionusing a relay has been introduced. The relay receives data from a basestation using the downlink sub-frame, and transmits the received data toa terminal using another downlink sub-frame.

Accordingly, the base station may transmit a control channel withrespect to the relay, as well as a control channel with respect to theterminal, using a downlink sub-frame. Since a number of control channelsto be transmitted via a downlink is increased, there is a desire for amethod of efficiently transmitting the control channels.

DISCLOSURE OF INVENTION Technical Goals

An aspect of the present invention provides a method of effectivelytransmitting and receiving a control channel in a wireless communicationsystem.

Technical Solutions

According to an aspect of an exemplary embodiment, there is provided amethod for operation of a base station, the method including allocatingdownlink allocation information to a downlink sub-frame, determiningwhether to transmit uplink allocation information using the downlinksub-frame, inserting, to the downlink allocation information based onthe determination, transmission information of uplink allocationinformation that includes information associated with whether totransmit the uplink allocation information, and transmitting thedownlink sub-frame to a terminal.

According to another aspect of an exemplary embodiment, there isprovided a method for operation of a terminal, the method includingreceiving a downlink sub-frame from a base station, extractingtransmission information of uplink allocation information from downlinkallocation information included in the downlink sub-frame, anddetermining whether uplink allocation information is included in thedownlink sub-frame, based on the transmission information of uplinkallocation information.

According to still another aspect of an exemplary embodiment, there isprovided a method for operation of a base station, the method includinggenerating a resource allocation indicator that includes informationassociated with a radio resource which has a possibility of being usedfor transmission of a physical downlink control channel (PDCCH), basedon a resource allocation scheme identifier that indicates informationassociated with a resource allocation type, and transmitting, to aterminal, the resource allocation indicator and the resource allocationscheme identifier, and the PDCCH is received based on the resourceallocation scheme identifier and the resource allocation indicator.

According to yet another aspect of an exemplary embodiment, there isprovided a method for operation of a terminal, the method includingreceiving a resource allocation indicator and a resource allocationscheme identifier from a base station, the resource allocation indicatorbeing generated based on the resource allocation scheme identifierindicating information associated with a resource allocation type,determining a radio resource which has a possibility of being used fortransmission of a downlink control channel transmitted from the basestation, based on the resource allocation indicator, and decoding thedownlink control channel in the radio resource.

Effect

According to example embodiments, there is provided a method ofeffectively transmitting and receiving a control channel in a wirelesscommunication system.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example of transmitting downlink allocationinformation and uplink allocation information using a downlinksub-frame;

FIG. 2 illustrates another example of transmitting downlink allocationinformation using a downlink sub-frame;

FIG. 3 illustrates an example where a base station transmits a physicaldownlink control channel (PDCCH) using a single unit resource;

FIG. 4 illustrates an example where a base station transmits a PDCCHusing four unit resources;

FIG. 5 illustrates an example where a base station transmits a PDCCHusing two unit resources;

FIGS. 6 through 11 illustrate an example where a base station allocatesa single unit resource set to a terminal, and the base station transmitsa PDCCH using a resource in the unit resource set;

FIG. 12 is a flowchart illustrating a method for operation of a basestation according to an embodiment;

FIG. 13 is a flowchart illustrating a method for operation of a terminalaccording to an embodiment;

FIG. 14 is a flowchart illustrating a method for operation of a basestation according to another embodiment; and

FIG. 15 is a flowchart illustrating a method for operation of a terminalaccording to another embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Although a few exemplary embodiments of the present invention have beenshown and described, the present invention is not limited to thedescribed exemplary embodiments, wherein like reference numerals referto the like elements throughout.

FIG. 1 illustrates an example of transmitting downlink allocationinformation and uplink allocation information using a downlinksub-frame, and FIG. 2 illustrates another example of transmittingdownlink allocation information using a downlink sub-frame.

The following embodiments of the present invention will be describedwith reference to FIGS. 1 and 2. It is assumed that a base stationtransmits the downlink allocation information and the uplink allocationinformation using a predetermined sub-frame 110 as illustrated in FIG.1, and the downlink allocation information and the uplink allocationinformation are located in a resource R1 120 and a resource R2 130,respectively. A downlink physical data channel indicated by the downlinkallocation information may be located in a resource R3 140.

Referring to FIG. 2, in a predetermined sub-frame, the base station maytransmit only downlink allocation information using a resource R1, andmay not transmit the uplink allocation information using a resource R2.In this example, to utilize the resource R2, the base station may alsotransmit downlink physical data channel using the resource R2. In thisexample, the downlink physical data channel may be allocated to theresource R2 and a resource R3.

In addition to the downlink allocation information, the uplinkallocation information, and the downlink physical data channel, anothersignal or another channel may be transmitted using the sub-frame 110.Also, downlink allocation information, uplink allocation information,and downlink physical data channels for different terminals may betransmitted using the sub-frame 110.

A bandwidth of the resource R1 120 that is used for transmission of thedownlink allocation information and a bandwidth of the resource R2 130that is used for transmission of the uplink allocation information maybe different. The resource R1 120 that is used for the transmission ofthe downlink allocation information may be divided into a plurality ofsmaller resources that are not close to each other in a frequency domainand in a time domain. A starting point of a time domain of the resourceR1 120 that is used for the transmission of the downlink allocationinformation may be different from a starting point of the sub-frame 110,and an end point of the time domain may be any point in time of thesub-frame 110. The resource R2 130 that is used for the transmission ofthe uplink allocation information may be divided into a plurality ofsmaller resources that are not close to each other in the frequencydomain and in the time domain. A starting point of a time domain of theresource R2 130 that is used for the transmission of the uplinkallocation information may be any point in time of the sub-frame 110,and an end point of the time domain may be different from an end pointof the sub-frame 110.

The resource R3 140 that is used for the transmission of the downlinkphysical data channel may be divided into a plurality of smallerresources that are not close to each other in the frequency domain andthe time domain. A starting point and an end point of a time domain ofthe resource R3 140 that is used for the transmission of the downlinkphysical data channel may be different from the starting point and theend point of the sub-frame, and may be different from the startingpoints and the end points of the resource R3 140 or the resource R2 130that are used for the transmission of the downlink allocationinformation and the uplink allocation information.

Referring to FIGS. 1 and 2, the base station may or may not transmit thedownlink physical data channel to the resource R2 130. The terminal maydetermine whether the downlink allocation information or the uplinkallocation information is transmitted based on whether decoding of thedownlink allocation information or the uplink allocation informationsucceeds. When the terminal fails in decoding the downlink allocationinformation or the uplink allocation information even though the basestation transmits the downlink allocation information or the uplinkallocation information, the terminal may determine that the downlinkallocation information or the uplink allocation information is nottransmitted.

In an aspect of the present invention, the downlink allocationinformation that uses the resource R1 120 and the uplink allocationinformation that uses the resource R2 130 may be associated with thesame terminal. Also, the downlink allocation information that uses theresource R1 120 and the uplink allocation information that uses theresource R2 130 may be associated with different terminals.

A case where the downlink allocation information that uses the resourceR1 120 and the uplink allocation information that uses the resource R2130 are associated with the same terminal will be described.

In an aspect of the present invention, the base station may transmit thedownlink allocation information and the uplink allocation information tothe terminal as illustrated in FIG. 1. The terminal may only succeed indecoding the downlink allocation information and may fail in decodingthe uplink allocation information. In this example, the terminal maydetermine that the uplink allocation information is not transmittedusing the resource R2 and the downlink physical data channel istransmitted using the resource R2 as illustrated in FIG. 3. In thisexample, the terminal may decode the downlink physical data channelusing the resource R2 130 and the resource R3 140, and, in most cases,may fail in the decoding.

In another aspect of the present invention, the base station maytransmit only the downlink allocation information to the terminal, andmay transmit downlink physical data channel using the resource R2, asillustrated in FIG. 2. The terminal may successfully decode the downlinkallocation information, and may succeed in decoding the uplinkallocation information. In this example, the terminal may determine thatthe uplink allocation information is transmitted using the resource R2130 and decode downlink physical data channel only using the resource R3140, and, in most cases, may fail in the decoding.

A case where the downlink allocation information that uses the resourceR1 120 and the uplink allocation information that uses the resource R2130 are associated with different terminals will be described.

In an aspect of the present invention, the base station may transmit thedownlink allocation information to a first terminal using the resourceR1 120, and may transmit the uplink allocation information to a secondterminal using the resource R2 130. The first terminal may succeed indecoding the downlink location information. However, the first terminalmay not decode the uplink allocation information transmitted to thesecond terminal. Even though the first terminal fails in decoding theuplink allocation information, the first terminal may not be able todetermine that the uplink allocation information is not transmittedusing the resource R2 130, and that the downlink physical data channelis transmitted using the resource R2 130, since the uplink allocationinformation may be transmitted using the resource R2 130, as describedin the forgoing.

The terminal needs to succeed in decoding the downlink allocationinformation and needs to be aware of whether the uplink allocationinformation is transmitted, to determine a location of a resource thatis used for transmission of the downlink physical data channel.

In an aspect of the present invention, the base station may transmit thedownlink allocation information that includes information indicatingwhether the uplink allocation information is transmitted or informationindicating whether the downlink physical data channel includes aresource which has a possibility of being used for transmission of theuplink allocation information. For ease of descriptions, the informationindicating whether the uplink allocation information is transmitted orinformation indicating whether the downlink physical data channelincludes the resource which has a possibility of being used fortransmission of the uplink allocation information may be referred to astransmission information of uplink allocation information.

The transmission information of uplink allocation information maydistinguish two or three different cases. When the transmissioninformation of uplink allocation information distinguishes two differentcases, the two different cases are as follows. In a first case, theuplink allocation information is not transmitted using the resource R2130, and the resource R2 130 is included in the downlink physical datachannel. In a second case, the uplink allocation information istransmitted using the resource R2 130, and the resource R2 130 isexcluded from the downlink physical data channel. In this example, theterminal may determine an aggregation level of the uplink allocationinformation by performing blind-decoding.

When the transmission information of uplink allocation informationdistinguishes three different cases, the three cases are as follows. Ina first case, the uplink allocation information is not transmitted usingthe resource R2 130 and the resource R2 130 is included in the downlinkphysical data channel. In a second case, the uplink allocationinformation allocated to the resource R2 130 with respect to the sameterminal indicated by the downlink allocation information, and theresource R2 130 is excluded from the downlink physical data channel. Inthis example, the terminal may determine an aggregation level of theuplink allocation information by performing blind-decoding. In a thirdcase, the uplink allocation information allocated to the resource R2 130with respect to the different terminal indicated by the downlinkallocation information, and the resource R2 130 is excluded from thedownlink physical data channel.

When the transmission information of uplink allocation informationdistinguishes a plurality of cases, the plurality of cases is asfollows. In a first case, the uplink allocation information is nottransmitted using resource R2 130, and the resource R2 130 is includedin the downlink physical data channel. In remaining cases, the uplinkallocation information is allocated to the R2 130 with respect to thesame terminal indicated by the downlink allocation information, and theresource R2 130 is excluded from the downlink physical data channel. Inthe remaining cases, an aggregation level of the uplink allocationinformation is different for each case.

For an example, when the transmission information of uplink allocationinformation distinguishes four different cases, an aggregation level ofthe uplink allocation information for a second case, a third case, and afourth case may be 2, 4, and 8 respectively.

In an aspect of the present invention, the base station may explicitlyadd the transmission information of uplink allocation information to thedownlink allocation information. The base station may add antransmission information of uplink allocation information bit field to adownlink allocation information bit field, and may perform transmission.The base station may not use a portion of the downlink allocationinformation bit field and may use the portion as the transmissioninformation of uplink allocation information bit field. When theterminal succeeds in decoding the downlink allocation information, theterminal may be aware of the transmission information of uplinkallocation information based on a value of the transmission informationof uplink allocation information bit field included in the downlinkallocation information.

When the transmission information of uplink allocation informationdistinguishes two different cases, the base station may allocate a 1 bitto the transmission information of uplink allocation information bitfield. Therefore, the transmission information of uplink allocationinformation may be expressed by ‘0’ or ‘1’. When the transmissioninformation of uplink allocation information distinguishes threedifferent cases, the base station may allocate two bits to thetransmission information of uplink allocation information bit field. Thetransmission information of uplink allocation information may beexpressed by three of ‘00’, ‘01’, ‘10’ and ‘11’. When the transmissioninformation of uplink allocation information distinguishes fourdifferent cases, the base station may allocate two bits to thetransmission information of uplink allocation information bit field. Thetransmission information of uplink allocation information may beexpressed by four of ‘00’, ‘01’, ‘10’ and ‘11’.

In another aspect of the present invention, the base station mayimplicitly transmit the transmission information of uplink allocationinformation. The base station may apply a predefined mask to a cyclicredundancy check (CRC) of the downlink allocation information, based onthe transmission information of uplink allocation information. Theterminal may apply a different predefined mask to the CRC of thedownlink allocation information when the terminal decodes the downlinkallocation information and thus, may be aware of the transmissioninformation of uplink allocation information. When the transmissioninformation of uplink allocation information distinguishes two differentcases, the base station and the terminal may use two differentpredefined masks. When the transmission information of uplink allocationinformation distinguishes three different cases, the base station andthe terminal may use three different predefined masks. As an example,when a length of the CRC is 16, a CRC mask may be as shown in Table 1 asfollows. The CRC mask of the present invention may not be limited toTable 1 and the length of the CRC and the mask may be different fromTable 1.

TABLE 1 CRC mask when a length of CRC is 16. CRC mask <x₀, x₁, . . . ,x₁₅> <0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0> <1, 1, 1, 1, 1, 1,1, 1, 1, 1, 1, 1, 1, 1, 1, 1> <0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1,0, 1>

The terminal may transmit information indicating a downlink wirelesschannel characteristic to the base station to inform the base station ofthe downlink wireless channel characteristic. The information indicatingthe downlink wireless channel characteristic may be a channel qualityindicator (CQI), a precoding matrix indicator (PMI), a rank indicator(RI), and the like. The base station may need some or all of the CQI,the PMI, and the RI. Accordingly, the base station may include aplurality of feedback modes that configures the downlink wirelesschannel characteristic that is to be transmitted by the terminal, to bedifferent from each other. The base station may transmit one of theplurality of feedback modes to the terminal, and the terminal may feedback the information indicating the downlink wireless channelcharacteristic, based on the received feedback mode. In an aspect of thepresent invention, the base station may transmit the feedback mode tothe terminal through higher layer signaling. According to the 3^(rd)generation partnership project (3 GPP), the higher layer signaling maybe RRC signaling. The terminal may transmit the information indicatingthe downlink wireless channel characteristic, based on the feedback modereceived from the base station.

The base station may transmit the downlink physical data channel to theterminal using a plurality of different transmission schemes, based on astate of a wireless channel. The plurality of transmission schemes mayinclude a space-time block code (STBC) scheme, an open loop spatialmultiplexing (SM) scheme, a closed loop SM scheme, a beamforming scheme,and the like. The base station may transmit a transmission mode to theterminal, and the transmission mode may be used when the base stationtransmits the downlink physical data channel to the terminal. In anaspect of the present invention, the base station may transmit thetransmission mode using the higher layer signaling. According to the3GPP, the higher layer signaling may be RRC signaling.

In an aspect of the present invention, each transmission scheme may beused as a transmission mode. In this example, the base station maytransmit the downlink physical data channel to the terminal using only asingle transmission scheme. Also, a plurality of transmission schemesmay be used as a single transmission mode. In this example, the basestation may transmit the downlink physical data channel to the terminalbased on the plurality of transmission schemes included in thetransmission mode. The terminal may decode the downlink physical datachannel based on the transmission mode received from the base station.

The base station may divide a total resource which has a possibility ofbeing used for transmission of a physical downlink control channel(PDCCH) into a plurality of divided resources, and some or all of theplurality of divided resources may overlap each other. In this example,the total resource which has a possibility of being used for thetransmission of the PDCCH may be referred to as a PDCCH total resource,and each of the plurality of divided resources may be referred to as aPDCCH group resource. A plurality of PDCCHs may be transmitted using thePDCCH group resource. The base station may transmit the PDCCHs using thesame or different schemes based on the PDCCH group resource. Forexample, the PDCCHs may be dispersively arranged in resources that arespaced away from each other, to obtain a diversity gain. For anotherexample, the PDCCHs may be arranged in adjacent resources, to obtain afrequency selective gain. In this example, the resource may beconstituted as a combination of a time resource, a frequency resource, aspace resource, a code resource, and the like. The present invention maynot be limited to the above described resource arrangement method.

The base station may transmit a location of the PDCCH total resource tothe terminal. Also, the PDCCH total resource may include a few PDCCHgroup resources, and the base station may transmit, to the terminal, alocation of each of the PDCCH group resources. The base station may alsotransmit, to the terminal, serial numbers assigned to each of the PDCCHgroup resources. In an aspect of the present invention, the base stationmay transmit, to the terminal, the information using higher layersignaling. According to the 3GPP, the higher layer signaling may be theRRC signaling.

The base station may transmit the PDCCH to the terminal in differentschemes based on a downlink wireless channel state. Accordingly, theterminal may not search the PDCCH total resource for the PDCCH, and maysearch a predetermined PDCCH group resource and thus, may reduce powerconsumption. The base station may inform the terminal of a serial numberof a PDCCH group resource which has a possibility of being used fortransmission of the PDCCH. The serial number of the PDCCH group resourcetransferred by the base station may be a single serial number or aplurality of serial numbers.

The base station may inform the terminal of the serial number of thePDCH group resource based on two methods. In a first method, the basestation directly transfers the serial number of the PDCCH group resourceto the terminal through higher layer signaling. According to the 3GPP,the higher layer signaling may be RRC signaling. In a second method, theserial number of the PDCCH group resource is connected to a transmissionmode or a feedback mode, and when the base station transmits thetransmission mode or the feedback mode to the terminal, the terminal mayindirectly recognize the serial number of the PDCCH group resource.

The base station may dispersively arrange the PDCCHs in resources thatare spaced away from each other, to obtain a diversity gain. The basestation may arrange the PDCCHs in adjacent resources, to obtain afrequency selective gain. In this example, the resource may beconstituted based on a combination of a time resource, a frequencyresource, a space resource, a code resource, and the like. The presentinvention may not be limited to the resource arrangement method in theforgoing. As described above, the PDCCHs may be transmitted in differentschemes.

Examples of the PDCCH may include a downlink allocation informationphysical control channel, an uplink allocation information physicalcontrol channel, and the like. A transmission scheme of the downlinkallocation information physical control channel and a transmissionscheme of the uplink allocation information physical control channel maybe determined based on a transmission of a downlink physical datachannel.

The PDCCH may include a plurality of resources, for example, a resourceelement (RE), a resource element group (REG), and the like in the 3GPP,and resources of PDCCHs with respect to different terminals may coexistin a single unit resource, for example, a physical resource block (PRB),a PRB-pair and the like, including a plurality of resources. A number ofunit resources including resources of PDCCHs for different terminals maybe determined based on a number of terminals included in a cell, atransmission scheme of a PDCCH, a utilization rate of resources, asystem bandwidth, and the like. For example, the number of unitresources including resources of PDCCHs for different terminals may beas shown in Table 2 as follows.

TABLE 2 Example of the number of unit resources including resources ofPDCCHs for different terminals N_(RB) ^(DL) SYSTEM BANDWIDTH NUMBER OFUNIT RESOURCES 6 15 25 50 75 100 [N_(RB) ^(DL)/5] 2 3 5 10 15 20 [N_(RB)^(DL)/10] 1 2 3 5 8 10 [N_(RB) ^(DL)/25] 1 1 1 2 3 4

Table 2 may also be expressed in the form of Table 3 as shown below. Theentries, ‘12’ and ‘18’, which indicate the number of unit resources inTable 3 are added, to decrease a difference between the number of unitresources corresponding to the respective entries.

TABLE 3 Example of the number of unit resources including resources ofPDCCHs for different terminals SYSTEM BANDWIDTH N_(RB) ^(DL) 6 15 25 5075 100 SET OF {1, 2} {1, 2, {1, 3, {2, 5, {3, 5, {4, 8, 10, NUMBER OF 3}5} 8, 10} 8, 10, 12, 15, 18, UNIT 12, 15} 20} RESOURCES

A number of resources that is used for transmission of the downlinkallocation information physical control channel among resources includedin the unit resources may be different from each other. When a number ofunit resources including resources of downlink allocation information ofphysical control channels for different terminals is equalized to anumber of unit resources including resources of uplink allocationinformation of physical control channels for different terminals,resources may be wasted. Therefore, to avoid waste of the resources, thenumber of unit resources including resources of downlink allocationinformation of physical control channels for different terminals may bedetermined to be different from the number of unit resources includingresources of uplink allocation information of physical control channelsfor different terminals.

The base station may transmit, to the terminal, the number of unitresources including resources of downlink allocation information ofphysical control channels for different terminals and the number of unitresources including resources of uplink allocation information ofphysical control channels for different terminals. In an aspect of thepresent invention, the base station may transmit the number of unitresources including resources of downlink allocation information ofphysical control channels for different terminals and the number of unitresources including resources of uplink allocation information ofphysical control channels for different terminals, through higher layersignaling. According to the 3GPP, the higher layer signaling may be RRCsignaling.

The base station may transmit only the number of unit resourcesincluding resources of downlink allocation information physical controlchannels for different terminals, and the terminal may derive the numberof unit resources including resources of uplink allocation informationof physical control channels for different terminals based on the valuereceived from the base station, and a ratio between a number ofresources included in the unit resources including resources of downlinkallocation information of physical control channels for differentterminals and a number of resources included in the unit resourcesincluding resources of uplink allocation information physical of controlchannels for different terminals.

The system bandwidth may include a plurality of unit resources, forexample, a plurality of PRBs in the 3GPP. A single sub-frame may includea plurality of unit resources. The plurality of unit resources may begrouped as a unit resource group, for example, a resource block group(RBG) in the 3GPP. For ease of description, a number of unit resourcesincluded in the unit resource group may be referred to as P, and P maybe 1, 2, 3, 4, and the like, which may vary based on the systembandwidth. A number of unit resources included in a last unit resourcegroup may be less than or equal to P, based on the system bandwidth. Thesystem bandwidth may include a plurality of unit resource groups, andthe unit resource groups constituting the system bandwidth may beclassified into P subsets. A number of unit resources included in thesystem bandwidth may be BW.

The base station may transmit, to the terminal, the PDCCH using one orthe plurality of unit resources. In an aspect of the present invention,the base station may transmit the PDCCH by utilizing one unit resourcefor each unit resource group. For example, the base station may transmitthe PDCCH by selecting a first unit resource, a second unit resource, athird unit resource, or a fourth unit resource among the plurality ofunit resources included in a unit resource group.

FIG. 3 illustrates an example where a base station transmits a PDCCHusing a single unit resource. FIG. 4 illustrates an example where thebase station transmits the PDCCH using four unit resources. FIG. 5illustrates an example where the base station transmits the PDCCH usingtwo unit resources.

When the base station transmits the PDCCH using the single unitresource, the PDCCH may be transmitted as illustrated in FIG. 3. Here,different patterns may indicate different PDCCHs. For ease ofdescription, FIG. 3 illustrates four PDCCHs and a maximum number ofPDCCHs may be ┌BW/P┐.

When the base station transmits, to the terminal, the PDCCH using aplurality of unit resources, the base station may transmit the PDCCHusing a unit resource group having the same subset.

When the base station transmits, to the terminal, the PDCCH using fourunit resources, an interval between unit resources that is used fortransmission of the PDCCH may be P2. In FIG. 4 different patterns mayindicate different PDCCHs. For ease of descriptions, FIG. 4 illustratesfour PDCCHs. A maximum number of PDCCHs may be ┌BW/(4P)┐.

When the base station transmits the PDCCH using two unit resources, aninterval between unit resources that is used for transmission of thePDCCH may be P² or 2P². In FIG. 5 different patterns may indicatedifferent PDCCHs. For ease of description, FIG. 5 illustrates twoPDCCHs. A maximum number of PDCCHs may be ┌BW/2P┐.

In an aspect to the present invention, the base station may transmit, tothe terminal, a location and a number of unit resources which have apossibility of being used for transmission of the PDCCH. In thisexample, the terminal may perform blind-decoding within an area that isused for transmission of the PDCCH which is received from the basestation, to search for the PDCCH.

In another aspect of the present invention, the base station may nottransmit the location and the number of unit resources which have apossibility of being used for transmission of the PDCCH. In thisexample, the terminal may perform blind-decoding with respect to a wholesystem bandwidth to search for the PDCCH. The terminal may performblind-decoding with respect to the whole bandwidth or a whole area thatis used for transmission of the PDCCH which is received from the basestation. When a search area dedicated by a terminal exists, the terminalmay perform blind-decoding with respect to a portion of the area or thesystem bandwidth that is used for transmission of the PDCCH.

The terminal may perform blind-decoding by changing a number of unitresources which have a possibility of being used for transmission of thePDCCH. The number of candidates which have a possibility of being usedfor transmission based on the number of unit resources which have apossibility of being used for transmission of the PDCCH.

The base station may transfer a resource which has a possibility ofbeing used for the transmission of the PDCCH, using a resourceallocation scheme identifier and a resource allocation indicator. Theresource allocation scheme identifier and the resource allocationindicator may be transferred through higher layer signaling, forexample, RRC signaling in the 3GPP. The resource allocation schemeidentifier and the resource allocation indicator may be configured basedon the following three schemes.

In a first scheme, the resource allocation scheme identifier identifiestwo cases that include a case indicating a resource allocation scheme 0or a resource allocation scheme 1 and a case indicating a resourceallocation scheme 2. In this example, the resource allocation schemes 0,1 and 2 may indicate resource allocation types 0, 1 and 2 of 3GPP TS36.212 and 3GPP TS 36.213, respectively.

In the first scheme, the resource allocation indicator may indicateresource allocation based on a resource allocation scheme indicated bythe resource allocation scheme identifier. When the resource allocationscheme identifier indicates the resource allocation scheme 0 or theresource allocation scheme 1, the resource allocation indicator may beconfigured to include a resource allocation header and a resource blockassignment of a DCI format 1 or a DCI format 2. In this example, the DCIformat 1 and the DCI format 2 may be defined in the 3GPP TS 36.212. Whenthe resource allocation scheme identifier indicates the resourceallocation scheme 2, the resource allocation indicator may be configuredto include a localized/distributed virtual resource block (VRB)assignment flag and a resource block assignment of a DCI format 1B or aDCI format 1D. In this example, the DCI format 1B and the DCI format 1Dmay be defined in the 3GPP TS 36.212. A bit size of the resourceallocation indicator may vary based on the resource allocation scheme 0,1 and 2 and a downlink system bandwidth.

In a second scheme, the resource allocation scheme identifier identifiesthree cases that include a case indicating the resource allocationscheme 0, a case indicating the resource allocation scheme 1 and a caseindicating the resource allocation scheme 2. In this example, theresource allocation schemes 0, 1 and 2 may indicate resource allocationtypes 0, 1 and 2 of 3GPP TS 36.212 and 3GPP TS 36.213, respectively.

In the second scheme, the resource allocation indicator may indicateresource allocation based on a resource allocation scheme indicated bythe resource allocation identifier. When the resource allocation schemeidentifier indicates the resource allocation scheme 0 or the resourceallocation scheme 1, the resource allocation indicator may be configuredto include the resource block assignment of the DCI format 1 or the DCIformat 2. Unlike the resource allocation indicator of the first scheme,the resource allocation header may not be included. In this example, theDCI format 1 and the DCI format 2 may be defined in the 3GPP TS 36.212.When the resource allocation scheme identifier indicates the resourceallocation scheme 2, the resource allocation indicator may be configuredto include the localized/distributed VRB assignment flag and theresource block assignment of the DCI format 1B or the DCI format 1D. Inthis example, the DCI format 1B and the DCI format 1D may be defined inthe 3GPP TS 36.212. A bit size of the resource allocation indicator mayvary based on the resource allocation schemes 0, 1 and 2 and thedownlink system bandwidth.

In a third scheme, the resource allocation scheme identifier identifiesfour cases including a case indicating the resource allocation scheme 0,a case indicating the resource allocation scheme 1, a case indicatingthe resource allocation scheme 2 and the localized VRB, and a caseindicating the resource allocation scheme 2 and the distributed VRB. Inthis example, the resource allocation schemes 0, 1 and 2 may indicatethe resource allocation types 0, 1 and 2 of the 3GPP TS 36.212 and 3GPPTS 36.213.

In the third scheme, the resource allocation indicator may indicateresource allocation based on a resource allocation scheme indicated bythe resource allocation scheme identifier. When the resource allocationscheme identifier indicates the resource allocation scheme 0 or theresource allocation scheme 1, the resource allocation indicator may beconfigured to include the resource block assignment of the DCI format 1or the DCI format 2. Unlike the resource allocation indicator of thefirst scheme, the resource allocation header may not be included. Inthis example, the DCI format 1 and the DCI format 2 may be defined inthe 3GPP TS 36.212. When the resource allocation scheme identifierindicates the resource allocation scheme 2, that is, when the resourceallocation scheme identifier indicates the resource allocation scheme 2and the localized VRB or indicates the resource allocation scheme andthe distributed VRB, the resource allocation indicator may be configuredto include the resource block assignment of the DCI format 1B or the DCIformat 1D. Unlike the resource allocation indicator of the first schemeand the second scheme, the localized/distributed VRB assignment flag maynot be included. In this example, the DCI format 1B and the DCI format1D may be defined in the 3GPP TS 36.212. A bit size of the resourceallocation indicator may vary based on the resource allocation schemes0, 1 and 2.

The terminal may recognize a resource of the PDCCH transmitted from thebase station based on the described schemes, and may performblind-decoding with respect to the resource to determine whether a PDCCHassociated with the terminal exists.

A transmission mode of a downlink physical data channel may be changedbased on a reference signal that is used for decoding of the downlinkphysical data channel Examples of the reference signal may include acell-specific reference signal (CRS) and a demodulation reference signal(DM-RS). When the same reference signal is used for decoding thedownlink physical data channel, a plurality of transmission modesassociated with the downlink physical data channel may be used.

When the reference signal used for decoding the downlink physical datachannel is the DM-RM, a location and a number of resources of the DM-RS,for example, a number of REs in the 3GPP, used in a single unitresource, for example, a PRB-pair in the 3GPP, may be different based ona number of antenna ports of the DM-RS. For an example, in the 3GPP,when the number of antenna ports of the DM-RS is one or two, twelve REsare used for each PRB-pair, and when the number of antenna ports of theDM-RS is in the range of three to eight, 24 REs are used for eachPRB-pair.

The location and the number of resources used for transmission of thePDCCH that is transmitted from the base station to the terminal may bedifferent based on the number of antenna ports of the DM-RS that is usedfor decoding the downlink physical data channel. Accordingly, theterminal may be able to decode the PDCCH when the terminal is aware ofthe number of antenna ports of the DM-RS that is used for decoding thedownlink physical data channel. The terminal may be aware of the numberof antenna ports of the DM-RS used for decoding the downlink physicaldata channel, through the PDCCH transmitted from the base station to theterminal. Accordingly, the base station may inform the terminal, inadvance, of the number of antenna ports of the DM-RS used for decodingthe downlink physical data channel.

The base station may inform the terminal of the number of antenna portsof the DM-RS used for decoding of the downlink physical data channelbased on two methods. A first method, which is an explicit method, maydirectly transfer the number of antenna ports of the DM-RS used fordecoding of the downlink physical data channel, through higher layersignaling. In the 3GPP, the higher layer signaling may be RRC signaling.In this example, the number of DM-RS antenna ports may be expressed bytwo cases. Here, the cases include, a case indicating the number ofantenna ports of the DM-RS is one or two and a case indicating thenumber of antenna ports of the DM-RS is three or more.

When the number of antenna ports of the DM-RS, which is transmitted bythe base station through the higher layer signaling, is one or two, theterminal may exclude a DM-RS resource of when the number of antennaports of the DM-RS is one or two, and may decode the PDCCH. When thenumber of the antenna ports of the DM-RS, which is transmitted by thebase station through the higher layer signaling, is three or more, theterminal may exclude a DM-RS resource of when the number of antennaports of the DM-RS is three or more, and may decode the PDCCH.

A second method, which is an implicit method, may indirectly transferthe number of antenna ports of the DM-RS used for decoding the downlinkphysical data channel, based on a transmission mode of the downlinkphysical data channel. The transmission mode associated with thedownlink physical data channel may be transferred through the higherlayer signaling. In the 3GPP, the higher layer signaling may be the RRCsignaling. When the reference signal used for decoding the downlinkphysical data channel is the DM-RS, a plurality of transmission modesassociated with the downlink physical data channel may be used. Thenumber of antenna ports of the DM-RS may be different based on thetransmission mode of the downlink physical data channel. A transmissionmode of the downlink physical data channel may use one or two antennaports of the DM-RS. Another transmission mode of the downlink physicaldata channel may use one to eight antenna ports of the DM-RS.

Therefore, when the base station transfers, to the terminal, atransmission mode of the downlink physical data channel that correspondsto the case where one or two antenna ports of the DM-RS are used, theterminal may exclude a DM-RS resource of when the number of antennaports of the DM-RS is one or two, and may decode the PDCCH. When thebase station transfers, to the terminal, a transmission mode of thedownlink physical data channel that corresponds to the case where one toeight antenna ports of the DM-RS are used, the terminal may exclude aDM-RS resource of when the number of antenna ports of the DM-RS is threeor more, and may decode the PDCCH.

FIGS. 6 through 11 illustrate an example where a base station allocatesa single unit resource set to a terminal, and the base station transmitsa PDCCH using a resource in the unit resource set.

The base station allocates the single unit resource set to the terminal,and may transmit the PDCCH using the resource included in the unitresource set. In the 3GPP, a unit resource may be a VRB. The unitresource sets may or may not be adjacent to each other in a frequencyband. The unit resource set for each terminal may be different, and thesame unit resource set may be allocated to different terminals.

An aggregation level may denote a number of unit resources used fortransmission of a single PDCCH and the aggregation level may configuredas an aggregation level 1, an aggregation level 2, an aggregation level4, an aggregation level 8 and the like. An area which has a possibilityof being used for transmission of PDCCH candidates, in a single unitresource set, may be referred to as a search space. A unit resourceindex of a search space where a PDCCH candidate m of which theaggregation level is L is located may be expressed as shown in Equation1.(L·(m×K _(L) i _(offset,L))+i)mod N  [Equation 1]

-   -   where i=0, 1, . . . , L−1 and m=0, 1, . . . M_(L)−1

In Equation 1, N denotes a number of unit resources included in a unitresource set that the base station transmits to the terminal, the unitresource index in the unit resource set may be 0, 1, . . . , and N−1. Lmay denote the aggregation level, m may denote an index of the PDCCHcandidate, i_(offset,L) and may denote a location offset of a PDCCHcandidate of when the aggregation level is L in the unit resource set.K_(L) may be a number of offsets, and may vary based on the aggregationlevel. i=0, 1, . . . , L−1 denotes that respective PDCCH candidateshaving the aggregation level of L are allocated to successive L unitresources within the unit resource set.

The number of PDCCH candidates having the aggregation level of L in thesearch space may vary based on a number of offsets, an aggregationlevel, and a number of unit resources included in the unit resource setthat the base station transmits to the terminal, which is expressed byEquation 2.

$\begin{matrix}{M_{L} = \left\lceil \frac{N}{L \times K_{L}} \right\rceil} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

In Equation 2, N denotes the number of unit resources included in theunit resource set, L denotes the aggregation level, M_(L) denotes thenumber of PDCCH candidates having the aggregation level of L. K_(L)denotes the number of offsets and may vary based on the aggregationlevel.

i_(offset,L), which denotes a location offset of a PDCCH candidate whenthe aggregation level is L in the unit resource set, may be expressed byEquation 3.i _(offset,L)=(ID)mod K _(L)  [Equation 3]

In this example, ID denotes an identifier assigned by the base stationto the terminal. In the 3GPP, the identifier may be a radio networktemporary identifier (RNTI) and thus, a cell-RNTI (C-RNTI), asemi-persistent scheduling C-RNTI (SPS C-RNTI), and the like may beused. K_(L) denotes the number of offsets, and may vary based on theaggregation level.

An embodiment of the present invention will be described with referenceto FIG. 6. It is assumed that the aggregation level is L=1, 2, 4, 8, thenumber of unit resources included in the unit resource set that the basestation transmits to the terminal is N=16, and the number of offsets isK₁=K₂=K₄=K₈=1. The number of PDCCH candidates (M_(L)) is M₁=16, M₂=8,M₄=4, and M₈=2. i_(offset,L) indicates the location offset of the PDCCHcandidate when the aggregation level is L in the unit resource set, mayalways be zero, regardless of the aggregation level and the identifierof the terminal. A location of the PDCCH candidate may be determinedbased on Equation 1 as shown in FIG. 6. A number included in a PDCCH ofFIG. 6 denotes m that is an index of the PDCCH candidate. A number ofunit resources that is used for transmission of a single PDCCH may beequivalent to the aggregation level.

An embodiment of the present invention will be described with referenceto FIG. 7. Here, it is assumed that the aggregation level is L=1, 2, 4,8, the number of unit resource sets that the base station transmits tothe terminal is N=16, and the number of offsets is K₁=K₂=K₄=K₈=2. M_(L)may be M₁=8, M₂=4, M₄=2, and M₈=1 based on Equation 2. Since theidentifier of the terminal is assumed to be an even number and thus,i_(offset,L) is L in the unit resource set and may bei_(offset,1)=i_(offset,2)=i_(offset,4)=i_(offset,8)=0 based on Equation3. A location of the PDCCH candidate may be determined based on Equation1 as shown in FIG. 7, based on Equation 1. A number included in a PDCCHof FIG. 7 denotes m which is an index of the PDCCH candidate. A numberof unit resources that is used for transmission of a single PDCCH may beequivalent to the aggregation level.

An embodiment of the present invention will be described with referenceto FIG. 8. It is assumed that the aggregation level is L=1, 2, 4, 8, thenumber of unit resources included in the unit resource set that the basestation transmits to the terminal is N=16, and the number of offsets isK₁=K₂=K₄=K₈=2. Also, an identifier of the terminal may be assumed to bean odd number. M_(L) may be M₁=8, M₂=4, M₄=2, and M₈=1, based onEquation 2. Since the identifier of the terminal is assumed to be theodd number and thus, i_(offset,L) that denotes the location offset ofthe PDCCH candidate of when the aggregation level is in the unitresource set may bei_(offset,1)=i_(offset,2)=i_(offset,4)=i_(offset,8)=1, based on Equation3. A location of the PDCCH candidate may be determined based on Equation1 as shown in FIG. 8. A number included in a PDCCH of FIG. 8 may denotem that is an index of the PDCCH candidate. A number of unit resourcesthat is used for transmission of a single PDCCH may be equivalent to theaggregation level.

An embodiment of the present invention will be described with referenceto FIG. 9. It is assumed that the aggregation level is L=1, 2, 4, 8, thenumber of unit resources included in the unit resource set that the basestation transmits to the terminal is N=16, the number of offsets isK₁=K₄=2 and K₂=K₈=1. Also, an identifier of the terminal is assumed tobe an odd number. M_(L) may be M₁=8, M₂=8, M₄=2, and M₈=2, based onEquation 2. Since the identifier of the terminal is assumed to be theodd number, i_(offset,L) that denotes the location offset of the PDCCHcandidate of when the aggregation level is L may bei_(offset,1)=i_(offset,4)=1 and i_(offset,2)=i_(offset,8)=0. A locationof the PDCCH candidate may be determined based on Equation 1 as shown inFIG. 9. A number included in a PDCCH of FIG. 9 denotes m in that is anin an index of the PDCCH candidate. A number of unit resources that isused for transmission of a single PDCCH may be equivalent to theaggregation level.

Even though it is assumed M_(L) that corresponding to the number ofPDCCH candidates of which the aggregation level is L in the search spaceis determined based on Equation 2, the present invention may alsoinclude randomly determining of M_(L) corresponding to the number ofPDCCH candidates of which the aggregation level is L in the searchspace. Even though it is assumed that i_(offset,L) that denotes thelocation offset of the PDCCH of when the aggregation level is L in theunit resource set is determined based on Equation 3, the presentinvention may also include directly transmitting i_(offset,L) from thebase station to the terminal through the higher layer signaling. In the3GPP, the higher layer signaling may be RRC signaling. The base stationmay transmit, to the terminal, the location offset of a PDCCH candidatefor each aggregation level. The base station may transmit, to theterminal, a location offset of a single PDCCH candidate that isequivalently applied to all aggregation levels.

The PDCCH candidate in the unit resource set that the base stationallocates to the terminal may be based on Equation 10 or Equation 11, asopposed to being based on Equation 1, Equation 2, and Equation 3. InEquation 10 and Equation 11, the aggregation level may be L=1, 2, 4, 8,and M₁=M₂=6 and M₄=M₈=2.

FIG. 12 illustrates a method for operation of a base station accordingto an embodiment.

In operation 1210, the base station allocates downlink allocationinformation to a downlink sub-frame. The downlink allocation informationmay be control information, and may include hybrid automatic repeatrequest information, a modulation and demodulation scheme, informationassociated with a location of a resource of a downlink physical datachannel transmitted from the base station to the terminal, and the like.

In operation 1220, the base station may determine whether to transmituplink allocation information using the downlink sub-frame. The uplinkallocation information may include hybrid automatic repeat requestinformation, a coding and decoding scheme, and information associatedwith a location of a resource of an uplink physical data channeltransmitted from the terminal to the base station, and the like. In thisexample, the resource may be configured as a combination of a timeresource, a frequency resource, a space resource, a code resource, andthe like.

When the base station determines to transmit the uplink allocationinformation using the downlink sub-frame, the base station may allocatethe uplink allocation information to the downlink sub-frame in operation1230. In an aspect of the present invention, the base station mayallocate the uplink allocation information to the same frequency band asthe downlink allocation information.

In an aspect of the present invention, a plurality of terminals mayaccess the base station. In this example, the downlink allocationinformation and the uplink allocation information may be associated withdifferent terminals with each other. The uplink allocation informationincluded in the downlink sub-frame may be allocation information withrespect to a first terminal included in the plurality of terminals, andthe downlink allocation information may be allocation information withrespect to a second terminal included the plurality of terminals.

The base station may insert transmission information of uplinkallocation information to the downlink allocation information inoperation 1240. The transmission information of uplink allocationinformation may be information indicating whether the uplink allocationinformation is transmitted using the downlink sub-frame.

The terminal may determine whether the uplink allocation information istransmitted using the downlink sub-frame, based on the transmissioninformation of uplink allocation information inserted to the downlinkcontrol information.

In an aspect of the present invention, the transmission information ofuplink allocation information may be explicitly transmitted. In thisexample, the base station may add an transmission information of uplinkallocation information bit field to a downlink allocation informationbit field included in the downlink sub-frame. The base station may notuse a portion of the downlink allocation information bit field and usethe portion as the transmission information of uplink allocationinformation bit field. The transmission information of uplink allocationinformation may be transmitted using the transmission information ofuplink allocation information bit field.

In another aspect of the present invention, the transmission informationof uplink allocation information may be implicitly transmitted. In thisexample, the base station may apply a mask to a CRC of the downlinkallocation information, based on whether the uplink allocationinformation is transmitted. Therefore, a value of the mask applied tothe CRC may be the transmission information of uplink allocationinformation.

In operation 1250, the base station may transmit the downlink sub-frameto the terminal.

FIG. 13 illustrates a method for operation of a terminal according to anembodiment.

In operation 1310, the terminal may receive a downlink sub-frame fromthe base station. The downlink sub-frame may include downlink allocationinformation. In an aspect of the present invention, the transmissioninformation of uplink allocation information may be included in thedownlink allocation information and may be transmitted.

In operation 1320, the terminal may extract transmission information ofuplink allocation information from the downlink allocation information.

In an aspect of the present invention, the transmission information ofuplink allocation information may be explicitly transmitted. In thisexample, the transmission information of uplink allocation informationmay be transmitted using an transmission information of uplinkallocation information bit field that is added to a downlink allocationinformation bit field included in the downlink sub-frame. Thetransmission information of uplink allocation information may betransmitted by using a portion of the downlink allocation informationbit field included in the downlink sub-frame as the transmissioninformation of uplink allocation information bit field.

In another aspect of the present invention, the transmission informationof uplink allocation information may be implicitly transmitted. In thisexample, the transmission information of uplink allocation informationmay be transmitted based on a mask that applies to a CRC. A value of thetransmission information of uplink allocation information may bedetermined based on a value of the mask applied to the CRC.

In operation 1330, the terminal may determine whether the uplinkallocation information is included in the downlink sub-frame, based onthe transmission information of uplink allocation information.

In operation 1340, the terminal may decode the uplink allocationinformation based on the determination in operation 1330. The uplinkallocation information may be allocated to the same frequency band asthe downlink allocation information.

The terminal may only decode the downlink allocation information, andmay determine whether the uplink allocation information is transmitted.Accordingly, when the uplink allocation information is not transmitted,unnecessary operations may not be performed and thus, power consumptionmay decrease.

FIG. 14 illustrates a method for operation of a base station accordingto another embodiment.

In operation 1410, the base station may determine a radio resource to beallocated to a terminal. The base station may determine a resourceallocation scheme that informs the terminal of the allocated radioresource. The base station may generate a resource allocation schemeidentifier based on the deter mined resource allocation scheme, and maygenerate a resource allocation indicator based on the resourceallocation scheme identifier. The resource allocation scheme identifiermay indicate information associated with a resource allocation type.

Examples will be provided based on the resource allocation schemeidentifier.

1) Resource allocation scheme identifier that identifies two cases.

In this example, the resource allocation scheme identifier may identifytwo cases that includes a first case where the resource allocation typeis ‘0’ or ‘1’ and a second case where the resource allocation type is‘2’.

When the resource allocation scheme identifier indicates that theresource allocation type is ‘0’ or ‘1’, the base station may configurethe resource allocation indicator to include a resource allocationheader and a resource block assignment of a DCI format 1 or a DCI format2 of the 3GPP TS 36.212.

When the resource allocation scheme identifier indicates that theresource allocation type is ‘2’, the base station may configure theresource allocation indicator to include a localized/distributed VRBassignment flag and a resource block assignment of a DCI format 1B or aDCI format 1D of the 3GPP TS 36.212.

A length of the resource allocation indicator, that is, a size of bitallocated to the resource allocation indicator, may vary based on avalue of the resource allocation type and the downlink system bandwidth.

2) Resource allocation scheme identifier that identifies three cases.

In this example, the resource allocation scheme identifier may identifyresource allocation types 0, 1 and 2.

When the resource allocation scheme identifier indicates that theresource allocation type is ‘0’ or ‘1’, the base station may configurethe resource allocation indicator to include the resource blockassignment of a DCI format 1 or a DCI format 2 of the 3GPP TS 36.212.

When the resource allocation scheme identifier indicates the resourceallocation type is ‘2’, the base station may configure the resourceallocation indicator to include the localized distributed VRB assignmentflag and the resource block assignment of the DCI format 1B or the DCIformat 1D of the 3GPP TS 36.212.

A length of the resource allocation indicator, that is, a size of bitallocated to the resource allocation indicator, may vary based on avalue of the resource allocation type and the downlink system bandwidth.

3) Resource allocation scheme identifier that identifies four cases.

In this example, the resource allocation scheme identifier may identifyfour cases that includes a case indicating that the resource allocationtype is ‘0’, a case indicating that the resource allocation type is ‘1’,a case indicating that the resource allocation type is ‘2’ andcorresponds to a localized VRB, and a case indicating that the resourceallocation type is ‘2’ and corresponds to a distributed VRB.

When the resource allocation scheme identifier indicates that theresource allocation type is ‘0’ or ‘1’, the base station may configurethe resource allocation indicator to include the resource blockassignment of the DCI format 1 or the DCI format 2 of the 3GPP TS36.212.

The resource allocation scheme identifier indicates that the resourceallocation type is ‘2’, the base station may configure the resourceallocation indicator to include the resource block assignment of the DCIformat 1B or the DCI format 1D of the 3GPP TS 36.212.

A length of the resource allocation indicator, that is, a size of bitallocated to the resource allocation indicator, may vary based on avalue of the resource allocation type and the downlink system bandwidth.

In operation 1420, the base station may transmit, to the terminal, theresource allocation scheme identifier and the resource allocationindicator. In an aspect of the present invention, the base station maytransmit the resource allocation scheme identifier and the resourceallocation indicator through the higher layer signaling, for example,RRC layer signaling.

The terminal may determine a radio resource which has a possibility ofbeing used for transmission of a PDCCH, based on the resource allocationscheme identifier and the resource allocation indicator. The terminalmay decode the PDCCH by performing blind-decoding of the radio resourcewhich has a possibility of being used for the transmission of the PDCCH.When the decoding succeeds, the terminal may determine that the PDCCH istransmitted.

The terminal may not search a whole downlink of radio resources andinstead may search radio resources in a predetermined area based on theresource allocation scheme identifier and the resource allocationindicator and thus, the terminal may not perform unnecessary operations.Accordingly, power consumption of the terminal may be reduced and alifespan of a battery may increase.

FIG. 15 illustrates a method for operation of a terminal according toanother embodiment.

In operation 1510, the terminal may receive, from a base station, aresource allocation indicator generated based on a resource allocationscheme identifier. The method of generating the resource allocationindicator based on the resource allocation scheme identifier has beendescribed with reference to FIG. 14 and thus, detailed descriptionsthereof will be omitted for conciseness.

In an aspect of the present invention, the terminal may receive theresource allocation indicator, through higher layer signaling, forexample, RRC signaling.

In operation 1520, the terminal may determine, based on the resourceallocation indicator, a radio resource which has a possibility of beingused for transmission of a PDCCH transmitted from the base station.

In operation 1530, the terminal may perform blind-decoding of the radioresource which has a possibility of being used for the transmission ofthe PDCCH. When the decoding succeeds, the terminal may determine thatthe PDCCH is transmitted.

The terminal may not search the whole downlink of radio resources, andinstead may search radio resources in a predetermined area based on theresource allocation scheme identifier and the resource allocationindicator and thus, the terminal may not perform unnecessary operations.Accordingly, power consumption of the terminal may decrease and alifespan of a battery may increase.

Although a few embodiments of the present invention have been shown anddescribed, the present invention is not limited to the describedembodiments. Instead, it would be appreciated by those skilled in theart that changes may be made to these embodiments without departing fromthe principles and spirit of the invention, the scope of which isdefined by the claims and their equivalents.

The invention claimed is:
 1. A method of transmitting controlinformation, the method comprising: configuring a resource allocationscheme identifier indicating a resource allocation type; configuring aresource allocation indicator indicating allocation information onresource for transmission of a downlink control channel according to theresource allocation type indicated by the resource allocation schemeidentifier; and transmitting to a receiver the resource allocationscheme identifier and the resource allocation indicator by upper layersignaling, wherein the resource allocation scheme identifierdistinguishes 4 or more types including resource allocation type 0,resource allocation type 1, resource allocation type 2 with localizedvirtual resource blocks, and resource allocation type 2 with distributedvirtual resource blocks, and wherein the resource allocation schemeidentifier and the resource allocation indicator are included in RRC(Radio Resource Control) signaling message transmitted from the basestation.
 2. The method of claim 1, wherein a size of the resourceallocation indicator is varied according to the resource allocationtype.
 3. A method of receiving control information, the methodcomprising: receiving a resource allocation scheme identifier indicatinga resource allocation type and a resource allocation indicatorindicating allocation information on resource for transmission of adownlink control channel according to the resource allocation typeindicated by the resource allocation scheme identifier; and decoding thedownlink control channel in the resource for transmission of downlinkcontrol channel based on the resource allocation scheme identifier andthe resource allocation indicator, wherein the resource allocationscheme identifier distinguishes 4 or more types including resourceallocation type 0, resource allocation type 1, resource allocation type2 with localized virtual resource blocks, and resource allocation type 2with distributed virtual resource blocks, and wherein the resourceallocation scheme identifier and the resource allocation indicator areincluded in RRC (Radio Resource Control) signaling message transmittedfrom the base station.
 4. The method of claim 1, wherein a size of theresource allocation indicator is varied according to system bandwidth.5. The method of claim 3, wherein a size of the resource allocationindicator is varied according to the resource allocation type and systembandwidth.